Television receiver safety interlock system for power connections

ABSTRACT

A simplified power interconnection is provided in a television receiver adapted for both battery and AC power operation and having a normally closed cabinet with a removable wall in the cabinet for access to the chassis by skilled service personnel. The power interconnection is fixed in the removable wall and has one connector pattern on the exterior of the wall which mates with disconnectable alternative battery and AC power source plugs outside the cabinet, and has a different connector pattern on the inside of the wall which mates with a single set of power connectors on the chassis inside the cabinet. Because the outside and inside mating patterns are different, unskilled personnel may alternatively energize the chassis through either of the power source plugs only when the removable wall is in position, and may not mate the loose power plugs to the chassis when the wall is removed.

United States Patent [72] Inventor Norman Surerny Portsmouth, Va. 7,555

Feb. 2, 1970 Dec. 21, 1971 General Electric Company [21] App]. No. [22] Filed [45] Patented [73] Assignee I54] TELEVISION RECEIVER SAFETY INTERLOCK SYSTEM FOR POWER CONNECTIONS 36, 37, 39, 59,119,125 R, 126 R, 126 RS, 127, 128, 129, 132, 133,134, 147 R, 147 C,l55, 156, 170,192 R; 174/52 R;178/7.8, 7.9; 179/1 PL,1 SW; 317/9 AI, 9 R, 99; 248/27 [56] References Cited UNlTED STATES PATENTS 2,265,341 12/1941 Borchert 339/170 X 339/32 M 2,296,839 9/1942 Draving 3,3 87,253 6/1968 Salners et a1 339/102 FOREIGN PATENTS 218,595 12/1961 Austria 339/126 R 927,514 5/1955 Germany 339/154A Primary Examiner-Marvin A. Champion Assistant ExaminerLawrence .l. Staab Attorneys-James E. Espe, Frank L. Neuhauser, Oscar B.

Waddell and Joseph B. Forman ABSTRACT: A simplified power interconnection is provided in a television receiver adapted for both battery and AC power operation and having a normally closed cabinet with a removable wall in the cabinet for access to the chassis by skilled service personnel. The power interconnection is fixed in the removable wall and has one connector pattern on the exterior of the wall which mates with disconnectable alternative battery and AC power source plugs outside the cabinet, and has a different connector pattern on the inside of the wall which mates with a single set of power connectors on the chassis inside the cabinet. Because the outside and inside mating patterns are different, unskilledpersonnel may alternatively energize the chassis through either of the power source plugs only when the removable wall is in position, and may not mate the loose power plugs to the chassis when the wall is removed.

PATENTEDDECEI 1971 3.6299789 SHEET 2 BF 2 A/ "7 94 5z6eEMy BY TELEVISION RECEIVER SAFETY INTERLOCK SYSTEM FOR POWER CONNECTIONS BACKGROUND OF THE INVENTION It is generally well known that, for reasons of safety, an interlock arrangement is provided in the power connections to a television receiver so that the power is automatically disconnected when the backwall of the receiver is removed. To discourage unskilled individuals from bypassing this interlock, the power cord connection at the receiver end is customarily permanently attached to the backwall so that the only way to connect power to the receiver chassis is to replace the backwall thus preventing the unskilled from obtaining access to the interior of the cabinet while the receiver is in operation.

With the advent of portable AC/DC transistorized TV sets operated from either external battery or normal AC power sources, consideration must now be given to how the dual power sources can be safely and economically connected to the set. For the purchaser's safety removal of the back must automatically disconnect the power from the chassis and it must be impossible without special equipment to bypass this interlock feature. At the same time, for protection of the set against accidental damage, it should not be possible to apply power to the chassis from both power sources at the same time. Unfortunately, the relatively high cost of internal sensing and switching devices required to meet the latter requirement mitigates against the permanent attachment of the AC and battery power cable to the backwall.

This invention is particularly directed to the foregoing problems in connection with transistorized television receivers which are powered alternatively by a battery plug connected to the cabinet, as in outdoor usage, or by a conventional 120- volt powerline plug connected to the cabinet as in indoor usage.

One arrangement hitherto used in this situation has been to use a four-terminal power receptacle on the outside of the cabinet. Into this receptacle either the battery plug using one set of two contacts of the four, or the powerline plug using the other set of two contacts of the four, is plugged in. With this arrangement, therefore, it is impossible to use more than one kind of power at a time, i.e., one cannot use both the battery plug and the 120-volt powerline plug at the same time.

The difficulty with the latter arrangement is that since the chassis uses only one power receptacle which has to mate with the two power plugs, these power plugs can be connected to the chassis even with the cabinet back removed. This is obviously unsafe since the unskilled user can power the chassis with the cabinet back removed.

STATEMENT OF THE INVENTION By fixing in the removable cabinet wall a double plug-receptacle which mates with the chassis inside the cabinet in one mating pattern, and which mates with the battery or powerline plugs outside the cabinet in a different mating pattern, this in vention makes it impossible to mate the battery or powerline plugs directly to the chassis. In other words, power may be applied to the chassis only when the removable wall is in position closing the cabinet.

DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a television receiver embodying the invention and powered alternatively through one or the other of two four-prong plugs, one plug being attached to a battery source of power as illustrated by FIG. 2, and the other plug being attached to a commonly available l-volt power source as illustrated by FIG. 3.

FIGS. 4, 5, 6 and 7 illustrate the manner in which a different plug mating pattern is used as between the inside and outside of the receiver.

FIGS. 8 and 9 show a mating pattern difference alternative to that of FIGS. 4 to 7.

7 DESCRIPTION OF THE PREFERRED EMBODIMENT .Referring to FIG. I, there is shown a television receiver 1 having the conventional cabinet 2 enclosing picture tube 3 as part of a chassis 4. The rear of the cabinet is normally closed by a backwall 5 which is fixed to the cabinet by screws 6 or removable from the cabinet by removal of screws 6 to permit access to the chassis and picture tube by skilled service personnel.

Power may be applied to the receiver I either from a battery 7 (FIG. 2) or l20-volt source 8 (FIG. 3) by way of four-contact female plug 9 connected to the battery 7 (FIG. 2) through cable 10, or by way of four-contact female plug II connected to source 8 (FIG. 3) through cable I2. Plugs 9 and 11 mate, one at a time, with four-contact male plug 13A fixed in wall 5. Note that in the four-contact pattern; of plugs 9 and II and plug 13A, the battery connects to the pair of small diameter contacts, while the l20-volt power source connects to the pair of larger diameter contacts. Since the plugs 9 and II can be mated with plug 13A only in the pattern shown, the battery can only be connected to battery circuits in the receiver, and the I20-volt source only to l20-volt circuits in the receiver. Only one of plugs 9 and Ill may be mated to plug 13A at a time and so only one kind of power may be applied to the receiver at a time.

Plug 13A is the outer part of a conductive interconnection 14 for interconnecting chassis 4 with either of plugs 9 and 11. This interconnection is affixed in removable wall 5 so that the unskilled user cannot remove it, or at least the user will be discouraged from doing so. The interconnection 14, which is shown better in the FIGS. 4 and 7, is designed so that the mating pattern between the interconnection l4 and the chassis 4 inside the cabinet is different from the mating pattern between the interconnection I4 and the plugs 9 and Ill outside the cabinet. Due to this difference it will be impossible for the unskilled user to mate the plugs 9 and 11 directly with the chassis 4 when the removable wall 5 is removed from the cabinet 2. In other words, the plugs 9 and II will not fit the chassis and it will be impossible for the user to apply power to the chassis so long as the removable wall 5 is not in position closing the receiver.

The foregoing purpose of different. mating patterns inside and outside the receiver 1 is accomplished in two ways in the FIGS. 4 to 9. In the FIGS. 4 to 7, it will be seen that the chassis 4 to interconnection l4 mating pattern is generally that of the four comers ofa square, while the interconnection 14 to plugs 9 and 11 mating pattern is that of the four corners of a trapezoid.

Thus, referring to FIGS. 4 and 7, it will be seen that the interconnection 14 comprises the male member 13A having four male prongs 15 which mate with the four female receptacles 16 of either of power plugs 9 and II; and a four-prong female member 138 having four female receptacles 17 which mate with a four-prong male member 18 on the chassis 4. As seen better in FIG. 5, the four-contact pattern between plugs 9 or II and member 13A outside the cabinet 2 is that of the four comers of a trapezoid; while as better seen in FIG. 6, the fourcontact pattern between the female receptacles I7 and the male prongs of member 18 on the chassis 4 is that of the four comers of a square. Thus, the female contacts of plugs 9 and II will not mate with male member 18 on the chassis because the trapezoidal and square patterns do not mate.

Corresponding female contacts 17 and male prongs 15 of the interconnection 14 may be permanently interconnected within interconnection M by any suitable means and interconnection I4 may be permanently secured to wall 5 by any suitable means as rivets l9. Interconnection 14 is shown as constructed of two members secured together by rivets 20 with suitable contacts ZI between corresponding prongs I5 and contacts 17. Member I8 is permanently secured to chassis 4 by rivets 22.

The male prongs of member 18 are of course connected by suitable means (not shown) to various elements of the chassis 4 requiring power from either battery 7 or l20-volt source 8.

In the embodiment of FIGS. 1 through 7, the plugs 9 and ll, and member 138 are female because their contacts 16 will have voltage upon them when cables 10 and 11 are connected to a power source and so will contacts 17 if contacts 16 and prongs 15 are connected together. The fact that plugs 9 and 11 and member 138 are female will minimize the possibility that the fingers of a user will touch the female contacts when so energized with voltage and when plugs 9 and 11 are disconnected from interconnection 14 or when plugs 9 and 11 are connected to interconnection 14 but backwall 5 is removed from cabinet 2. To further minimize the possibility that the fingers of the user will touch the female contacts 16 and 17, those contacts are, as shown in FIG. 7, positioned well within the interior of plugs 9 and 11, and member 13B.

While the plugs 9 and 11 and member 138 are shown as female, and members 13A and 18 as male, plugs 9 and 11 and member 138 may be replaced by male members and members 13A and 18 by female members. But in that case, it will be necessary to provide suitable protective shields around the male prongs of plugs 9 and 11 and member 13B in order to minimize the possibility that the fingers of the user may touch the male prongs of plugs 9 and 11 and member 138 when energized with voltage and separated from the cabinet under the conditions previously described. Such a shield is illustrated in no. 8. I

Alternatively, as in FIGS. 8 and 9, the different mating patterns may be brought about by arranging the male-female relationship in reverse order as between the inside and outside of the cabinet. Thus, as illustrated in FIG. 9, both inner and outer terminals of interconnection 14 are male; while the chassis member 18 and plugs 9 and 11 are both female and thus cannot be directly interconnected. In this arrangement, both inside and outside contact patterns may be the trapezoidal patterns illustrated in FIG. 8, or the square pattern previously mentioned, or any other pattern.

In FIG. 9, a cylindrical shield 23 is provided surrounding the inner male members of interconnection 14 for the purpose of minimizing the possibility that the fingers of the user may touch the male prongs within the shield 23 when voltage is on those prongs as when one of the plugs 9 or 11 is connected both to the power source through cables 10 or 12 and to the male prongs outside wall 5 when wall 5 is removed from cabinet 2. Shield 23 will, of course, slide over member 18 so that the male prongs may engage the female contacts on the chassis.

The FIG. 9 construction may be altered so that both sides of interconnection 14 are female and member 18 and plugs 9 and 11 are male. In that case, shield 23 would be placed around the male prongs of plugs 9 and 11 for the same purpose as before.

lt will thus be seen that the invention provides a means whereby the unskilled user may not apply power to the receiver unless he has the removable wall in safe position closing the cabinet. It should discourage him from making the attempt to do his own servicing while power is on the receiver. Moreover, the arrangement is very inexpensive.

It will be understood that the invention is useful in other than television receivers-for example, radio sound receivers, or any electrical or electronic devices which are alternately powered by either battery or powerline source.

lclaim:

1. In an electrical device having a normally closed cabinet enclosing electrical equipment to isolate it from unskilled personnel, the cabinet having a wall removable for access to the equipment by skilled service personnel, the equipment being adapted to be energized through a mateablepower plug connection externally of the cabinet to a conductive interconnection extending through the removable wall, and the interconnection being mateable to the electrical equipment internally of the cabinet;

such a conductive interconnection adapted to supply two different modes of electrical power to different portions of the electrical equipment, said conductive interconnection adapted to extend through and be fixed to the removable wall, said conductive interconnection comprising:

a first set of at least three contact means disposed in a first pattern at a first side of said conductive interconnection and adapted to engage a first or a second pair of power plug contact means;

a second set of at least three contact means disposed in a second pattern at a second side of said conductive interconnection and adapted to engage a corresponding set of mating contact means for supplying power to the two different portions of the electrical equipment;

whereby the power plug contacts cannot be mated to said mating contact means within the cabinet and cannot energize the electrical equipment except through the conductive interconnection.

2. An interconnection as in claim 1 in which the contact means are male and female contacts and the difference in mating patterns comprises a difference in cross-sectional positioning of the male and female contacts.

3. An interconnection as in claim 2 in which:

the power plug is female;

the conductive interconnection is male externally of the cabinet and female internally of the cabinet;

and the electrical equipment is male.

4. An interconnection as in claim 1 in which the contact means are male and female contacts, said power plug contacts being of the same sex as said contact means within the cabinet.

5. In an electrical device having a normally closed cabinet enclosing electrical equipment to isolate it from unskilled personnel, the cabinet having a wall removable for access to the equipment by skilled services personnel, the equipment having a portion adapted to be energized through a plug connected to a source of direct current electrical power and another portion adapted to be energized through a plug connected to a source of alternating current electrical power, the plugs being mateable externally of the cabinet to a conductive interconnection through the removable wall, and the interconnection being mateable to the electrical equipment internally of the cabinet, such a conductive interconnection adapted to extend through and be fixed in the removable wall, comprising:

a first plurality of contacts for mating the plugs to the conductive interconnection externally of the cabinet in a given mating pattern;

a second plurality of contacts each electrically connected to ones of the first plurality of contacts for mating the conductive interconnection to the electrical equipment within the cabinet adapted to be energized by direct current electrical power;

a third plurality of contacts each electrically connected to others of the first plurality of contacts for mating the conductive interconnection to the electrical equipment within the cabinet adapted to be energized by alternating current electrical power;

said second and third pluralities of contacts being disposed in a mating pattern different from that of said first plurality of contacts.

6. An interconnection as in claim 5 in which the contacts are male and female and the difference in mating patterns comprises a difference in cross-sectional positioning of the male and female contacts.

7. An interconnection as in claim 6 in which:

the plugs are female;

the conductive interconnection is male externally of the cabinet and female internally of the cabinet;

and the electrical equipment is male.

8. An interconnection as in claim 5 in which the contact means are male and female contacts, said power plug contacts being of the same sex as said contact means within the cabinet. 

1. In an electrical device having a normally closed cabinet enclosing electrical equipment to isolate it from unskilled personnel, the cabinet having a wall removable for access to the equipment by skilled service personnel, the equipment being adapted to be energized through a mateable power plug connection externally of the cabinet to a conductive interconnection extending through the removable wall, and the interconnection being mateable to the electrical equipment internally of the cabinet; such a conductive interconnection adapted to supply two different modes of electrical power to different portions of the electrical equipment, said conductive interconnection adapted to extend through and be fixed to the removable wall, said conductive interconnection comprising: a first set of at least three contact means disposed in a first pattern at a first side of said conductive interconnection and adapted to engage a first or a second pair of power plug contact means; a second set of at least three contact means disposed in a second pattern at a second side of said conductive interconnection and adapted to engage a corresponding set of mating contact means for supplying power to the two different portions of the electrical equipment; whereby the power plug contacts cannot be mated to said mating contact means within the cabinet and cannot energize the electrical equipment except through the conductive interconnection.
 2. An interconnection as in claim 1 in which the contact means are male and female contacts and the difference in mating patterns comprises a difference in cross-sectional positioning of the male and female contacts.
 3. An interconnection as in claim 2 in which: the power plug is female; the conductive interconnection is male externally of the cabinet and female internally of the cabinet; and the electrical equipment is male.
 4. An interconnection as in claim 1 in which the contact means are male and female contacts, said power plug contacts being of the same sex as said contact means within the cabinet.
 5. In an electrical device having a normally closed cabinet enclosing electrical equipment to isolate it from unskilled personnel, the cabinet having a wall removable for access to the equipment by skilled services personnel, the equipment having a portion adapted to be energized through a plug connected to a source of direct current electrical power and another portion adapted to be energized through a plug connected to a source of alternating current electrical power, the plugs being mateable externally of the cabinet to a conductive interconnection through the removable wall, and the interconnection being mateable to the electrical equipment internally of the cabinet, such a conductive interconnection adapted to extend through and be fixed in the removable wall, comprising: a first plurality of contacts for mating the plugs to the conductive interconnection externally of the cabinet in a given mating pattern; a second plurality of contacts each electrically connected to ones of the first plurality of contacts for mating the conductive interconnection to the electrical equipment within the cabinet adapted to be energized by direct current electrical power; a third plurality of contacts each electrically connected to others of the first plurality of contacts for mating the conductive interconnection to the electrical equipment within the cabinet adapted to be energized by alternating current electrical power; said second and third pluralities of contacts being disposed in a mating pattern different from that of said first plurality of contacts.
 6. An interconnection as in claim 5 in which the contacts are male and female and the difference in mating patterns comprises a difference in cross-sectional positioning of the male and female contacts.
 7. An interconnection as in claim 6 in which: the plugs are female; the conductive interconnection is male externally of the cabinet and female internally of the cabinet; and the electrical equipment is male.
 8. An interconnection as in claim 5 in which the contact means are male and female contacts, said power plug contacts being of the same sex as said contact means within the cabinet. 